1. Field of the Invention
This invention relates to valve apparatus and, more particularly, to a double valve apparatus usable in a swimming pool environment for introducing chlorine gas into a water line when the swimming pool motor is on to pump water for the filtration system.
2. Description of the Prior Art
Chlorine gas is typically introduced into a swimming pool through a venturi. The venturi is disposed in the swimming pool water system generally downstream of the filter, the heater, and any other elements which may be in series with the swimming pool pump. Depending on the particular system, back pressure may allow water to flow into the chlorine line, or the system may lose prime if air is introduced into the system. That is, when the pump turns off, the venturi may cause air to be introduced into the system, thus allowing air to flow backwards through the pump, and the pump will then lose its prime.
The apparatus of the present invention overcomes the problems of the prior art by using pool water pressure to open a pilot valve, and the valve closes when the pressure is removed from the pilot valve. Positive pressure from the pump is required to open the valve. However, the valve closes merely by the vacuum pressure of the head of water in the line to prevent the introduction of air into the system. At the same time, a second valve also closes. Moreover, any back pressure in the system will also cause the second valve to close to prevent water from flowing backwards into the chlorine gas line.